1. Field of the Invention
The present invention relates generally to the field of medical devices and in particular to the field of long term, implantable devices for permitting access to a patient's inner physiology.
2. Summary of the Related Art
Medically treating a patient often requires long term placement of a medical device across one or more organ systems to establish access to a specifically targeted interior body site for diagnostic or therapeutic purposes. One common example is the establishment of percutaneous vascular access for purposes of administering liquid therapeutic agents, removing bodily fluids for testing or monitoring, treating bodily fluids before being returned to the body, and/or disposing of bodily fluids.
Particularly in the case of administering fluids to, or removing fluids from, the body continuously or periodically over an extended time period, those skilled in the medical arts typically use what are known as “permanent” catheterization techniques. These techniques employ implanted devices such as tunneled central venous catheters (CVCs) that remain implanted for durations ranging from a few weeks to years. Examples of such implanted and related medical devices exist in the following references, which are incorporated herein by reference: U.S. Pat. No. 4,266,999 (Baier); U.S. Pat. No. 4,405,305 (Stephen et al.); U.S. Pat. No. 4,488,877 (Klein et al.); U.S. Pat. No. 4,668,222 (Poirier); U.S. Pat. No. 4,897,081 (Poirier et al.); U.S. Pat. No. 4,935,004 (Cruz); U.S. Pat. No. 5,098,397 (Svensson et al.); U.S. Pat. No. 5,100,392 (Orth et al.); U.S. Pat. No. 5,242,415 (Kantrowitz et al.); U.S. Pat. No. 5,662,616 (Bousquet); U.S. Pat. No. 5,823,994 (Sharkey et al.); U.S. Pat. No. 5,830,184 (Basta); U.S. Pat. No. 5,848,987 (Baudino et al.); U.S. Pat. No. 5,882,341 (Bousquet); U.S. Pat. No. 5,989,213 (Maginot); and U.S. Pat. No. 6,033,382 (Basta). Examples of therapeutic regimens requiring such long-term continuous or periodic access to a specific internal body location include parenteral feeding, chemotherapy, antibiotic administration, dialysis, and chronic anesthesiology.
Generally, the type of procedure that a patient requires dictates whether a physician will utilize an acute, short term catheterization technique, or a chronic, long term catheterization technique. For example, establishing a state of general anesthesiology in preparation for a surgical procedure typically involves placing a CVC in a patient's blood vessel for a relatively short period of time, such as a few minutes to a few hours, and then removing the catheter once the surgery is finished and the patient is revived. When performing such an anesthesiology procedure, a physician commonly uses a short term catheterization technique to place a drug delivery catheter in a blood vessel of the patient.
In direct contrast to this example of short term CVC placement, a physician performing a hemodialysis procedure in a patient suffering from chronic kidney failure may place a CVC in one of the patient's blood vessels for a relatively long period of time. Such a patient typically requires dialysis sessions three times per week for an indefinitely extended period of time. Healthy kidney function ensures removal of fluid, chemicals, and wastes typically filtered from a person's blood. Hemodialysis removes these elements by sending a patient's blood to an external artificial kidney machine via the permanent vascular access, often established by placement of a long term catheter within the patient. A patient who is involved in such a hemodialysis regimen may need a catheter placed in a blood vessel for weeks, months, or years in order to provide a ready means for vascular access into that patient's bloodstream to enable these frequent life saving dialysis treatments.
Long term catheterization techniques typically entail inserting a catheter into a patient using a “tunneled catheter technique.” This procedure involves inserting a long term catheter into the patient through an incision in the skin and then routing the catheter for several centimeters under the skin before entering deeper regions of the body. Despite routine use, conventional tunneled catheter designs seriously compromise the ability of a patient's skin to protect the patient's body from infection. As discussed in “Intravascular Catheter-Related Infections: New Horizons and Recent Advances” (Raad et al., Arch Internal Medicine/Vol 162, Apr. 22 2002, Pages 871-878.), catheter-related infections are frequent events and present a potentially fatal health problem. High morbidity rate and high procedural cost are characteristics of typical long term tunneled catheter usage. The primary reason that the use of conventional catheters leads to a high rate of infection is that microorganisms enter the body through the skin incision. A conventional tunneled catheter device may include a tissue ingrowth cuff that acts as a barrier for micro-organisms entering the body and that anchors the catheter in the subcutaneous tunnel. Such a conventional device, however, still fails to prevent undesirably high infection rates. This is because standard cuff designs are designed for positioning within a subcutaneous tunnel rather than at the skin entry site, which is the most effective location at which to position a tissue ingrowth cuff for preventing infection.
Furthermore, in order to function properly over extended periods of time, many types of long term tunneled catheters require placement of their tips in a very specific high blood flow location, typically the Superior Vena Cava/Right Atrial Junction (SVC/RA). The turbulent flow in this location ensures rapid mixing and systemic distribution of therapeutic agents throughout a patient's vascular system, and also minimizes the risk of thrombus forming on the catheter's tip and leading to catheter dysfunction. Skilled clinicians are acutely aware of the need for highly precise catheter tip placement because they frequently diagnose and resolve catheter complications associated with improper tip placement. With conventional tunneled catheter designs, the ability to precisely adjust the position of the catheter tip in the SVC/RA depends largely on a freedom to position and adjust the tissue ingrowth cuff anywhere along the length of a subcutaneous tunnel.
Some tunneled catheter devices include adjustable dermal tissue ingrowth cuff assemblies. For example, the apparatus and methods disclosed in U.S. Patent Application No. 2004/0236314 to Mark A. Saab (Saab), incorporated herein by reference, allow a physician to place a modular dermal tissue ingrowth cuff assembly precisely within a skin incision site and subsequently adjust the location of the distal (internal) tip of a catheter assembly associated with the tissue ingrowth cuff assembly. This device comprises a base (or port) having tissue ingrowth material thereon for securely anchoring the port at the incision site. A physician using such a device, therefore, has the ability to position the catheter tip precisely at the desired body site without disturbing, moving, or stressing the fixed tissue ingrowth cuff. Positioning the modular tissue ingrowth cuff at the skin incision site enables the skin to heal into the device, and regain its ability to protect the patient from infection.
Such advanced tissue ingrowth cuff assemblies have resulted in numerous improvements related to patient care and well being, but they fail to anticipate or address several practical implementation issues. First, these existing devices typically require one or more conduit connections to the port (base) to establish a continuous and reliable sealed fluid path between the inner and outer regions of the patient's body. A clinician implanting such a device and connecting conduits to the base (port) disposed within a subcutaneous pocket is unable to see the connection points during assembly and after assembly to ensure proper, secure connections. This problem is increasingly serious with small devices because the clinician loses a significant tactile advantage during assembly. Second, incorporating multiple connection mechanisms into the base (port) complicates assembly and creates more junctions at which the device may fail. Third, having multiple mechanical connections to the base (port) prolongs the medical procedure and unnecessarily complicates the adjustment of the device to suit a patient's physiology. Also, these devices fail to enable a clinician to determine where to trim the conduit to ensure proper distal tip placement within a patient's anatomy. Requiring a clinician to connect one or more elements to the port therefore increases difficulty of use, increases manufacturing cost, prolongs the medical procedure, and, most importantly, decreases reliability of the device.
A need therefore exists for a subcutaneous port that anchors a transcutaneous conduit, protects a patient from infection, and requires no conduit fluid path connections to the port. Furthermore, in cases requiring modular conduit, for example when the distal tip requires precise placement, a need exists for a device that supports a modular conduit having a single fluid path connection point inside the patient's physiology. A further need exists for a device that enables making and testing that conduit-to-conduit connection for proper assembly outside the patient's body within a clinician's view prior to positioning the connected modular conduit inside the patient's physiology. Lastly, a need exists for a device that facilitates using a simple and precise method of predetermining where to trim the conduit along its length prior to making the conduit-to-conduit connection to ensure proper final distal tip placement.